Currently, liquid crystal display devices have been widely used in various electronic products to serve as display components of electronic devices. Since liquid crystal cannot emit light by itself, a backlight module is needed to provide a light source for the liquid crystal display device. Therefore, the backlight module is an essential component in the liquid crystal display device. A common backlight module includes components mainly of a reflective sheet, a light guide plate, an optical film assembly and a backlight source.
With the advancement of science technologies, a technology of integrating functional modules and a touch function comes into being. Such functional modules include a fingerprint module, a sensing module, etc. Taking a fingerprint module for example, the invisible fingerprint sensor (IFS) technology is to adhere a fingerprint recognition module directly below a touch screen glass panel to achieve an integrated appearance design of a front a front screen panel without forming any through hole at the front surface or the back surface of a mobile phone, thereby not only having a touch function but also achieving waterproof and dustproof effects. In comparison to the conventional fingerprint recognition technology, in the IFS technology, the fingerprint sensor senses fingerprint information directly through the glass cover and the display screen. On this basis, a method of forming a through hole the positions of the light guide plate, the reflective sheet, the optical film assembly of the backlight module corresponding to the fingerprint sensor is proposed for transmission of fingerprint information. However, in such backlight module, the functional module will block the illumination light that is emitted by the backlight source, which results in a darker area at the back surface of the light guide plate and thereby causes the liquid crystal display device to display non-uniform images.